Mortar Calculator — How Much Mortar Mix Do I Need?

How to Calculate Mortar Quantity

Mortar volume depends on the application type and the joint size. The general approach is to estimate the volume of all joints in the assembly:

• Bricklaying: ~0.0035 cubic feet of mortar per standard brick
• CMU block laying: ~0.012 cubic feet of mortar per standard block
• Tile setting: ~1 cubic foot per 15 square feet of tile
• Stucco / parging: ~1 cubic foot per 12 square feet

One standard 80 lb bag of mortar mix yields approximately 0.5 cubic feet of mixed mortar. Always add a 15% waste allowance to account for waste during mixing and application.

Mortar Mix Types & When to Use Each

• Type S: High strength (1,800 psi). Below-grade masonry, retaining walls, in-ground work.
• Type N: Medium strength (750 psi). General-purpose above-grade exterior masonry.
• Type M: Very high strength (2,500 psi). Foundations, driveways, hardscaping in contact with earth.
• Type O: Low strength (350 psi). Interior, non-load-bearing walls and repointing.
• Modified thin-set: For floor and wall tile over concrete or cement board.

Always use the mortar type recommended by the block, brick or tile manufacturer. Using a mortar that is too strong for the masonry unit can cause cracking.

Mixing & Application Tips

Properly mixed mortar is critical for a durable installation. Follow these guidelines:

• Mix mortar to a stiff, workable consistency — it should hold its shape when squeezed
• Use clean, potable water and clean mixing equipment
• Do not re-temper mortar that has started to set; discard and mix a fresh batch
• Hot or windy weather accelerates drying — mist new work and cover overnight
• Cold weather (below 40°F / 4°C) requires heated materials and cold-weather protection

Frequently Asked Questions